Volume 537 Issue 7622



News Features

Can Cuban science go global? p.600

Tensions between Cuba and the United States are easing. But researchers still struggle to join the scientific world.

doi: 10.1038/537600a

News & Views

Hybrid vigour characterized p.620

Crossing different plant varieties to improve yield and fertility is common practice. A dissection of the genomic architecture that underlies such hybrid vigour might help to inform future crop-improvement strategies. See Article p.629

doi: 10.1038/nature19433

MRI illuminated by γ-rays p.621

A technique that combines magnetic resonance with nuclear medicine has been used to image the distribution of a radioactive tracer, potentially opening up a powerful and innovative approach to medical imaging. See Letter p.652

doi: 10.1038/537621a

The bacterial cell wall takes centre stage p.622

An unexpected function has been assigned to part of the molecular machinery that synthesizes the bacterial cell wall — a dramatic shift in our understanding that may have major implications for antibiotic development. See Article p.634

doi: 10.1038/537622a

A collaboration worth its weight in grain p.624

Interventions to improve crop yields in rural China through collaboration between researchers and farmers illustrate how the goal of increasing global food production can be approached locally. See Letter p.671

doi: 10.1038/nature19431

Long-term effects of permafrost thaw p.625

Carbon emissions from the Arctic tundra could increase drastically as global warming thaws permafrost. Clues now obtained about the long-term effects of such thawing on carbon dioxide emissions highlight the need for more data.

doi: 10.1038/537625a

Forecast for water balance p.626

Disturbances in internal water equilibrium can be debilitating for mammals. Two studies pinpoint areas of the mouse brain that respond to and anticipate thirst, preserving systematic fluid regulation. See Letters p.680 & p.685

doi: 10.1038/537626a

Small molecular replicators go organic p.627

The emergence of complex, dynamic molecular behaviour might have had a role in the origin of life. Such behaviour has now been seen in a reaction network involving small, organic, self-replicating molecules of biological relevance. See Letter p.656

doi: 10.1038/537627a


The architecture of the mammalian respirasome p.639

Respirasomes are supercomplexes of mitochondrial electron transport chain complexes that are responsible for cellular respiration and energy production; a cryo-electron microscopy structural study of the respirasome is presented.

doi: 10.1038/nature19359

The architecture of respiratory supercomplexes p.644

Respirasomes are supercomplexes of mitochondrial electron transport chain complexes that are responsible for cellular respiration and energy production; cryo-electron microscopy structures of mammalian (sheep) respirasomes are presented.

doi: 10.1038/nature19774


The awakening of a classical nova from hibernation p.649

Long-term pre- and post-eruption observations of the classical nova V1213 Centauri reveal that its progenitor was a dwarf nova and that the mass-transfer rate increased considerably as a result of the nova explosion.

doi: 10.1038/nature19066

A method for imaging and spectroscopy using γ-rays and magnetic resonance p.652

Magnetic resonance imaging (MRI) provides fine spatial resolution, spectral sensitivity and a rich variety of contrast mechanisms for diagnostic medical applications. Nuclear imaging using γ-ray cameras offers the benefits of using small quantities of radioactive tracers that seek specific targets of interest within the body. Here we describe an imaging and spectroscopic modality that combines favourable aspects of both approaches. Spatial information is encoded into the spin orientations of tiny amounts of a polarized radioactive tracer using pulses of both radio-frequency electromagnetic radiation and magnetic-field gradients, as in MRI. However, rather than detecting weak radio-frequency signals, imaging information is obtained through the detection of γ-rays. A single γ-ray detector can be used to acquire an image; no γ-ray camera is needed. We demonstrate the feasibility of our technique by producing images and spectra from a glass cell containing only about 4 × 1013 atoms (about 1 millicurie) of the metastable isomer 131mXe that were polarized using the laser technique of spin-exchange optical pumping. If the cell had instead been filled with water and imaged using conventional MRI, then it would have contained more than 1024 water molecules. The high sensitivity of our modality expands the breadth of applications of magnetic resonance, and could lead to a new class of radioactive tracers.

doi: 10.1038/nature19775